The goal of these studies is to define the molecular events which regulate normal erythroid cell development. A series of mutants in beta globin biosynthesis, the beta thalassemias and related disorders are being studied in order to define the defect in DNA structure, and the changes in beta globin mRNA biosynthesis which accompany these disorders. Restriction endonuclease analysis has already defined deletions of all or part of the delta and beta globin structural genes in some rarer forms of thalassemia, delta beta thalassemia and hereditary persistence of fetal hemoglobin (HPFH). However, restriction enzyme analysis of DNA from several patients with beta plus and beta zero thalassemia from Mediterranean populations has thus far failed to reveal differences in the restriction endonuclease digestion patterns. This may be due to the relatively small changes in DNA accompanying these disorders, which go undetected by restriction endonuclease analysis. Therefore, studies have begun in which unfractionated human cellular DNA has been used to specifically clone the beta and delta human globin genes. This cloning has utilized charon 4A lambda phage DNA as the vector and E. coli DP50SupF as host. Clones have already been obtained which contain the complete delta and beta genes from a patient with beta plus thalassemia, and this DNA is available for comparison with that of cloned DNA from a non-thalassemia patient. These DNAs have been compared directly by extensive restriction endonuclease analysis and are currently being studied by direct nucleotide sequencing using the Maxam-Gilbert procedure. The analysis of several normal DNAs, and beta plus and beta zero thalassemia DNAs, should define the changes in globin gene DNA structure which are important for globin gene expression in man.